In this investigation of early environmental influences on cognitive and personality development during the first year of life, one major goal has been to develop an observational instrument to analyze the components of the early environment. A second objective was to study relationships between specific parameters of the environment and specific aspects of development during the first six months. The sample consisted of 41 black infants - 21 boys and 20 girls - and their primary care-givers on whom we had a representative sample of their early experiences. These families were largely of lower socioeconomic status. Data on environmental variables were obtained through time-sampling observations in the natural environment of the home when the infants were 5 months of age. Measures of infant characteristics were obtained by means of the Bayley Scales of Infant Development and a structured situational test designed to measure exploratory behavior and preference for novel stimuli. In addition to the Mental Developmental Index and the Psychomotor Developmental Index, eight clusters of items were derived from the Bayley Scales: Gross Motor Development, Fine Motor Development, Social Responsiveness, Language, Goal Directedness, Secondary Circular Reactions, Reaching and Grasping, and Object Permanence. The major findings of this study are presented in detail in a book published this year, "Infant and environment: Early cognitive and motivational development."